This invention pertains to the synthesis of amides using amine carbamic acid salts and more particularly to the use of alkylamine carbamic acid salts as well as aralkylamine carbamic acid salts to effect this end.
Organic amides have found widespread industrial application as solvents and especially as aprotic polar solvents. The long-chain fatty acid amides are currently used as anti-block and anti-slip agents for ethylene polymers and as surfactants. Ethylenically unsaturated dibasic acid amides, particularly maleic acid diamide and fumaric acid diamide are monomers used in various addition and condensation polymerizations. Other diamides have found utility as chelating agents.
Prior art methods of preparing amides have included the acylation of amines, as described by M. L. Bender in Chem. Rev. 60; 53, (1960); "The Chemistry of Amides," by J. Zabiscky, page 75, Interscience Publishers, N.Y.C., (1970); and by J. Hipkin et al., J. Chem. Soc. (B), 345, (1946). This method requires that a carboxylic acid derivative which activates the molecule to react with an amine. Acyl halides, esters and anhydrides have been used as the carboxylic acid derivative as shown below in the respective equations. ##STR1##
A second prior art means for synthesizing amides is the amination of carboxylic acids described by H. Schindlbauer et al., Synthesis 11, 634 (1962), J. K. Lawson, Jr. et al., J. Org. Chem. 28, 232 (1963), and J. F. Brauzier et al., Bull. Soc. Chim. France (6), 2109 (1966). Several variations of this method are delineated in the following equations. ##STR2##
In all of the above equations R, R.sub.1, R.sub.2 and R' are alkyl groups.
While the above-described methods provide a variety of amides, they exhibit several drawbacks, viz.,:
(1) Require a derivative preparation step. PA1 (2) Require the use of solvents for the reaction. PA1 (3) Generate solid by-products and therefore disposal problems. PA1 (4) Require catalysts, complicated extraction steps and tedious purification steps. PA1 (1) carboxylic acid anhydrides having the formula ##STR5## wherein R" is an dialkylene ether or a divalent aliphatic radical having 1 to about 4 carbons, o-phenylene or o-cyclohexylene radicals; PA1 (2) carboxylic acids having the formula EQU R--COOH PA1 wherein R is H, alkyl having 1 to about 20 carbons or --R'--COOH wherein R' is alkylene having 1 to about 18 carbons; and PA1 (3) carboxylic acid esters having the formula EQU R--COOR.sub.2 PA1 wherein R is as defined above and R.sub.2 is alkyl having 1 to about 8 carbons. PA1 methyl formate PA1 ethyl-2-phenoxy acetate PA1 ethyl formate PA1 methyl acetate PA1 ethyl acetate PA1 propyl propionate PA1 butyl acetate PA1 methyl butyrate PA1 ethyl pentanoate PA1 propyl octanoate PA1 ethyl laurate PA1 hexyl acetate PA1 lauryl propionate PA1 octadecyl formate, and the like.
A third method of preparing amides has also been used and is described by E. R. Shephard et al. in J. Org. Chem. 17, 568 (1952). This is a thermal dehydration of the ammonium salt formed by the interaction of a carboxylic acid and an amine as shown below. ##STR3##
This method suffers the drawbacks of requiring excessive heating at high temperatures and often necessitates the use of metal oxide catalysts. In addition the use of amine reagents tends to affect the unsaturated moieties of carboxylic substrates containing such moieties.
It is therefore an object of this invention to provide an improved process for the preparation of organic amides free of the defects of the prior art techniques.
Other objects will become apparent to those skilled in the art upon a further reading of the specification.